Many articles of manufacture require that metal members be attached to one another to form various structures. The fuselage of an aircraft and the body of an automobile are examples of such structures that are fabricated by joining one or more metal members. There are many different ways of joining metal members together, one of which involves the use of metal rivets which form a mechanical connection between the two metal members.
There are many different types of rivets that can be used to join metal members together. One type of rivet is a self-piercing rivet. Self-piercing rivets typically have a head and a shaft that is hollow along at least an end portion opposite the head. In some embodiments, the end portion is sharpened to permit the self-piercing rivet to pierce metal members.
In a conventional procedure, the sharpened end portion is placed against two (or more) stacked metal members (the “workpiece”) and driven into the workpiece by a punch. A die, having a protrusion, is placed opposite the punch below the workpiece. As the self-piercing rivet is driven towards the die, the sharpened end portion pierces completely through the first metal member and partially through the second metal member. At the same time, the protrusion on the die causes the second metal member to deform outwardly towards the self-piercing rivet. This causes the self-piercing rivet to deform at its end portion, creating an upset or bent portion that secures the self-piercing rivet to the workpiece and the metal members to one another.
If an unsuitable die is used during this process or if the self-piercing rivet is not properly aligned with the die, an improperly joined or discrepant joint may be formed. For example, in some cases, the self-piercing rivet may not be driven completely through the first metal member. In other cases, only a part of the end portion may be driven into the second member. In still other cases, the end portion of the self-piercing rivet may not be properly upset. In these cases, the self-piercing rivet will fail to properly join the stacked metal members or it may lack the robust connection that would have resulted had the die and the self-piercing rivet been properly aligned.
Solutions to this issue involve removing the improperly-installed-self-piercing rivet from the workpiece and installing a new self-piercing rivet at either the same location on the workpiece, or at a nearby location. Repairing discrepant joints in this manner, while adequate, can be difficult, time consuming, costly, and can risk damaging the workpiece.